The present invention relates to the metering of fluids at low flow rates.
More particularly, the invention provides a flow regulator for flows as low as about ½ ml per hour, now provided with locking means for any set value within its range.
The present invention is a development of, and an improvement on our previous patent U.S. Pat. No. 6,598,618 B1, which is hereby incorporated herein by reference.
Although the flow regulator made according to our previous patent '618 has been used successfully, there has been some user feedback which demanded thorough consideration. The lack of a locking means is thought to have prevented patients from going home while still needing medication, as the doctor in charge could not be assured that the patient would be receiving the required dosage, not more and not less. The resulting longer stay in hospital is detrimental to the patient and expensive for those paying for health care. Even while the patient is still hospitalized there are cases of a medicine being infused into a patient wherein an increased dosage would endanger the life thereof. In such cases the medical team is understandably averse to assuming that nobody will tamper with the flowmeter. Also, some users reported difficulty in turning the outer hollow housing, in order to adjust the flow rate, while at the same time restraining revolution of the core member.
These concerns are the major factors which are addressed by the present application.
A search for prior art regarding the period since our '618 patent was published revealed little new in the field of low-flow regulators.
About half a year before the publication of our '618 patent, a US patent application to Effenhauser et al, US2002/0087110A1 was published. This application discloses an evaporation type pump for exceedingly low-flow tasks in the range of 1 to 1000 nl/min. Larger flows which are often needed for liquid infusions are of course not possible with this type of pump.
Calderon in US Patent Application No. 2005/0010077 discloses a “Low-flow atrial-arterial shunt for pump-assisted myocardial revascularization without cardiopulmonary bypass.” The blood-containing tube disclosed is to be placed in a peristaltic pump, thus making the device unsuitable for monitoring very low flows and unlike the regulator of the present application.